werner and k



V. G. WERNER AND K. H. WARFVINGE, INDUCTIVE WIRELESS'TELEPHONE SYSTEMFOR HAILROADS AND THE LIKE. APPLICATION FILED MAY 10. 11916.

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lPadzemen'iAug. 5, W19,

V. G. WERNER AND K. H. WARFVl-NGB INDUCTIVE WIRELESS TELEPHONE SYSTEMFOR RAILROADS AND THE mun APPLICATION FILED MAYIO. 19m.

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VICTUR GABRIEL WERNER, OF BODEN, AND

HJ'ALMAIL WARJEVING-E, 0F

STQCKHOLM, SWEDEN.

IND'UC'IIVE WiRELESS TELEPHONE SYSTEM FOR RAIlLROADS AND THE LIKE.

To all whom it may concern:

Be it known that we, V1c'r0R GABRIEL WERNER and KARL HJALMAR WAnrvmcn,subjects of the King of Sweden, and residents, respectively, of Bodenand of Stockholm, in the Kingdom ofSweden, have invented a new anduseful Improvement in lnductive Wireless Telephone Systems for Railroadsand the like, of which the ing is a specification.

This 7 invention relates to an inductive wireless telephone system fortelephonic communication between a moving railroad train, or othervehicle, and a railroad station, or other stationary place, of the kindin which on the vehicle, a circuit comprising a' 'microphone, a receiverand a source of current, which circuit is in inductive relation toanother stationary circuit consisting of a single or double aerialconductor along the track and connected with a stationary telephonestation. In an arrangement of this kind a .very substantial reduction ofthe cost of erection will be attained if the telegraph or telephonewires usually present along the railway track may be used for thestationary circuit, or if. this can not be done, thenecessary specialaerial conductor may be attached'to the poles of the telegraph ortelephone line. As the distance, however, between the train and thetelegraph or telephone lines along the track is rather great, as a rule,and as this distance owing to trafiic-technical reasons can .not bereduced below a certain limit, it is necessary, in order to attain apracticable result, to use with the stationarytelephone apparatus aswell as with the moving apparatus, microphones of a certain kind,socalled strong-current microphones, which are capable of convertingsubstantially greater quantitiesof energy into oscillations of speechfrequency, than it is possible with ordinary microphones. The insertionof a strong-current microphone in the stationary circuit has the efiect,however, that ad'acent circuits are subjected to disturbances yinduction which renders theirluse vastly more difficult, whentelephoning to or from the train.

The present invention has for its 'ob ect to eliminate this disadvantae, and it is broadly characterized by this t conductor of the stationarycircuit is Specification of Letters Patent.

followthere is arranged on the train, orv

when during certain conditions at the aerial Patented Aug. 5, i919.

Application filed May 10,1916. Serial No. 96,491.

vided into two equal or approximately equal parts or branches connectedin parallel and extending in opposite directions from the fixed station,which is connected. with the point or points of union of the twobranches of the" conductor or conductors. The currents in the twobranches which extend in opposite directions, may then by means ofsuitable regulation be made to exert an equally strong inductiveinfluence, but in opposite directions so'that the disturbing effects ofinduction on adjacent lines will be come balanced. At the same time theadvantage is attained that the influence of earth-currents on the twobranches will equalize each other as regards the receiving apparatus,which fact is of particular importance when there is a single aerialconductor, the earth being used as return conductor.

branches of the aerial conductor must be v made of different lengths, orif for other reasons their inductive influences on adj acent linesbecome of different strengths, the desired freedom from disturbance maybe obtained by connecting a fixed or a variable resistance in the branchwhich has the strongest disturbing influence. In the case that theinductive disturbances on adjacent conductors are of less consequence,the arrangement may be used for completely equalizing the disturbingefiects of the earth-currents.

In the accompanying drawings Figures 1 to 12 show diagrammaticallydifi'erent embodiments of the invention. Fig. 1 shows an embodiment inwhich a single wire conductor especially erected, is used. Fig. 2 showsan embodiment in which the stationary circuit is formed by a section ofan ordinary telegraph line wire, and Fig. 3 shows a similar embodimentwith several stations. Fig; lshows asimilar embodiment with'a telegraphstation' included in the stationary cir cuit. [Fig 5 shows an embodimentusin 7 cuit.

applied to several stations, and Fig. 11

shows an embodiment in which the fixe station is disconnected.

Fig. 1 shows an embodiment in which a single wire aerial conductor !ABespecially erected along the track is used, the two end points A and Bof the same being point C of fixed telestation is circuit-changer 1, bymeans the strong-current microsource 3 of current or the be connectedinto the cir- The station on the train is provided in known manner withan induction frame the conductor and the earth the phone station isconnected. This provided with a of which either phone 2 with itsreceiver 4 may 5, which is preferably mounted around the roof of arailroad car and which may be connected by means of a circuit-changer 6either with the strong-current microphone 7 and its source 8 of currentor with the receiver 9. As shown in the drawing the aerial conductor isdivided into two equal branches CA and C-B which are connected inparallel and which run in opposite directions from the fixed station,whereby the advantages referred to above are at tained.

In the following figures the entire fixed station or stations arereferenced D, D, D

' etc., and the movable station (on the train) is referenced E, E Eetc., for the sake of simplicity.

In the embodiment shown in Fig. 2 the stationary circuit is formed by asection A C -B of an ordinary single wire telegraph line T-T and of aspecial conductor 101112 which is suitably erected on the other side ofthe track in regard to the telegraph line, the end oints of the samebeing connected with the opposite points A and B of said line. dle ofthe section the fixed station D is connected between the points C and11. The station D-will thus be located in one of the diagonals of aWheatstone bridge, the sides of which are formed by the lengths C B B12,11, 1110 and A C hence it becomes without current as regards thetelegraph currents, rovided that the resistances in the said sides arechosen properly. A variable resistance 13 is inserted in the length11-12 in order to render possible I regulation in this respect.

bridge, while the other two Fig. 3 illustrates this last describedarrangement applied to a plurality of fixed stations D each of which isconnected in a diagonal of a Wheatstone bridge. The telegraph line T Tforms two sides of each sides are formed byspecial conductors 110l12.

In Fig. 4. another modification of the ar rangement according to Fig. 2is illustrated which is proposed for the case that the section of thetelegraph line A B used inresistances of the difierent parts .anyappreciable degree.

About at the midf phone line.

cludes a telegraph station F at the fixed telephone station D Thestation F is shunted by means of two condensers 14 connected in series,and the telephone station D is connected between the point of connectionbetween these condensers and the middle point 211 of the conductor210-212. Each of the connections A 210 and B 212 comprises a condenser15. \Vhen the of the circult have been properly chosen, the station D?becomes without current in regard to at least the most rapid Variationsin the telegraph currents.

In the arrangement according to Fig. 5 each of the two end points A andB of the section of the telegraph line TT- used for telephoning, isgrounded through a condenser 16 and 17. The choke coils 18 and 19 whichare connected in the telegraph line beyond the points A and B and thecondensers 20 and 21 which are inserted between points in the telegraphline beyond said choke coils, and the ground, serve in known manner forflattening the telegraph currents in the range A -B and for preventingthe telephone currents from extending beyond this range. 'The telephonestation D which is connected in series with a condenser 22 insertedbetween the same and the telegraph line, is connected between theapproximate middle point C of the section A -B and the ground, and owingto the flattening of the telegraph currents it does not become disturbedby these currents to The variable rcslstance 23 serves for the samepurpose as the resistance 13 shown in Fig. 2.

Fig. 6 shows how a double wire telephone line may be used for formingthe stationary circuit, of which the length A-C*-B orms the aerialconductor. At each end point of this length a choke coil 24 and 25provided with an iron core is connected between the two Wires of thetelephone line, the middle points of these coils being grounded. At thestation C, which is located about at the middle of the length A*-B, asimilar choke coil 26 is connected between the wires of the telephoneline,'the' fixed tele hone station D being connected between tl iemiddle point of this coil and the earth. In conformity with theconditions of duplex connection of a telephone line between two fixedstations, and on account of the symmetry of the new circuit formed inregard to the two Wires of the telephone line used, the new circuitbecomes undisturbed as regards the ordinary trafiic on the tele- Only avery small portion of the speech currents inthe telephone line isshort-circuited or led off through the choke coils, which offer only avery small resistance. however, to the currents in the new inductivecircuit, as these currents divide double wire telephone themselves onthe two halves of the choke coils in such manner that the two branchcurrents equalize each others induction in the iron cores of the coils.

Fig. 7 shows the same arrangement as Fig. 6, the only difference beingthat a variable resistance 27, which as regards action corresponds tothe resistance 13 in Fig. 2, is inserted between the choke coil25 andthe earth.

According to Fig. 8 this variable resistance consists of two equal parts28 and 29, each of which is connected to one wire of the line A -C- B-".'lhese resistances are preferably arranged in such manner that whenthere is no communication to or from the train, the resistances areshort-circuited by means of the contacts 30 and 31, which are operatedby means of the hook 32 provided for the receiver of the fixed station DIn the arrangement according to Fig. 9 the variable resistance consistsof two coils 33 and 34: bifilar wound on a common iron core, each ofsaid coils being connected to one wire of the telephone line in suchmanner that the currents directed in opposite directions, which currentsrepresent the ordinary traffic on the telephone line, equalize eachothers induction on the iron core. On the other hand, the coils form apowerful inductive resistance to one branch current of the new inductivecircuit.

Fig. 10 illustrates the arrangement according to Fig. 6 applied to aplurality of stations D, which are connected to the same double wiretelephone line A-B". The stations are arrang d in such manner that theyare automatical y short -circuited when not in use. As soon as areceiver is lifted up at any station, a branched circuit is formed whichextends to the adjacent station on each side, and the inductive actionof which on adjacent lines is equalized, if desired by means of variableresistances connected in the circuit. The stations are short-circuitedby means of the hooks 35 for the receivers.

Fig. 11 illustrates an embodiment in which the fixed station D isdisconnected, the primary winding 37 of a transformer being connected in'its place between the middle point of the choke coil 36 and the earth,the secondary winding 38 of which transformer is connected between thetwo wires of the double wire telephone line A -B", or to a specialtelephone line which connects the station I)? with another station D Thecurrents induced in the stationary circuit by the circuits on the trainwill thus not be received at the station D", but will become transformedin the transformer 37, 38 and will thence be conducted by the doublewire telephone line to a station on the railroad beyond the groundedsection of the line, or through a special telephone line to a telephonestation not on the railroad. By switching ofi the station D in thismanner it is thus possible substantially to increase the range withinwhich it is possible to obtain telephonic communication with the movingrailroad train.

Fig. 12 shows an embodiment of the invention which consists of acombination of the features illustrated in Figs. 2, 8 and 9 and in whicha metallic conductor 10-11-- 12 is substituted for the earth connectionbetween the middle points of the choke coils.

We claim: I

1. In an inductive wireless telephone system for railroads, thecombination of a circuit on the train comprising a microphone, areceiver, and a source of current, and a stationary circuit in inductiverelation to the first named circuit and comprising an aerial line alongthe railroad track connected to a fixed telephone station, said aerialline being divided into two approximately equal branches connected inparallel and extending in opposite directions from the fixed telephonestation, for the purpose of equalizing disturbing inductive effects onadjacent circuits and also disturbances caused by earth-currents,substantially as described.

2. In an inductive wireless telephone system for railroads, thecombination of a circuit on the train comprising a microphone, areceiver, and a source of current, a stationary circuit in inductiverelation to the firstnained circuit and comprising an aerial line alonthe railroad track connected to a fixed 100 telep ione station, saidaerial line being divided into two approximately equal branchesconnected in parallel and extending in opposite directions from thefixed telephone station, and a variable resistance connected to 105 oneof said branches, substantially as, and for the purpose set forth.

3. In an inductive wireless telephone system for'railroads, thecombination of a circuit on the train comprising a microphone, a 110receiver and a source of current, and a stationary circuit in inductiverelation to the first named circuit and comprising a section of anaerial line along the railroad track and a conductor connected at itsends to the end 115 points of the said section, and a fixed telephonestation connected between the approximate middle point of the saidsection and the approximate middle point of the said conductor,substantially as and for the 120 purpose set forth. i

4. In an inductive wireless telephone sys-. tem for railroads, thecombination of a circuit on the train comprising a microphone, areceiver and a source of current, and asta 12 tionary circuit ininductive relation to the gfirst named circuit and comprising a section,said choke coils being connected together, a ehoke coil connectedbetween the two wires at the approximate middle point of said section,and a fixed telephone station connected between the middle of said chokecoil-and the connection between the middlepoints of the two'choke coilsfirst mentioned, substantially as and for the purpose setforth.

5. In an inductive wireless telephone system for railroads, thecombination of a circuit on the-train comprising a microphone,a receiverand a sourceof current, and a stationarycircuit in inductive relation tothe first named circuit and comprising a section,

of a double wire telephone line, choke coils connected between the twowires at the end points of said section, the middle points of said chokecoils being connected together, a variable resistance comprising twoequal parts one of which is connected to each wire of the section, achoke coil connected between the two wires at the approximate mid,-.

connected between the two wires at the end points of said section, theniddle. points of mate middle pointof said'section, and a fixed chokecoils being connected together, a

telephone station connected between the middle of said choke coil andthe connection becomprising two equal I tween the middle points of thetwo choke coils first mentioned, substantially as and for the purposeset forth.

7. In an inductive wireless telephone system for railroads, thecombination of a circuit on the train comprising a microphone, areceiver and. a source of current, and a stationary first named circuitand comprising a section of a'double wire telephone line, choke coilsconnected between the two wires at the end points of said section, themiddle points of said choke coils being connected together, a variableresistance comprising two bifilar wound coils one of which is connectedto each wire of the section, a choke coil connected betweenthe two wiresat the approximate middle point of said section, and a fixed telephonestation connected between the middle of said choke coil and theconnection between the middle points of the two choke coils firstmentioned, substantially as and for the purpose set forth.

VICTOR GABRIEL WERNER. KA RL HJALMAR WARFVINGE.

circuit in inductive relation to the

